Double container

ABSTRACT

A double container includes an inner container and an outer container, has a mouth portion, a body portion and a bottom portion disposed in this order from top to bottom along a direction of a bottle axis, and includes an outside air introduction hole. The bottom wall portion of the bottom portion includes a ground contact portion and a recessed portion. A peripheral wall portion of the depressed portion extends inward in a radial direction as it goes upward. A plurality of ridge portions protruding radially inward are provided on the peripheral wall portion of the depressed portion at intervals in a circumferential direction. The peripheral wall portion of the depressed portion or the ridge portion extends inward in the radial direction via a step portion as it goes upward.

TECHNICAL FIELD

The present invention relates to a double container. Priority is claimed on Japanese Patent Application Nos. 2020-130571, filed Jul. 31, 2020, 2021-056425 filed Mar. 30, 2021, and 2020-130566 filed Jul. 31, 2020, the contents of which are incorporated herein by reference.

BACKGROUND ART

From the related art, a double container is known which includes an inner container that decreases in volume and deforms with a decrease in contents therein, and an outer container in which the inner container is installed, has a mouth portion, a body portion, and a bottom portion disposed in this order from top to bottom along a direction of a bottle axis, and includes an outside air introduction hole that introduces outside air between the outer container and the inner container with the decrease in contents. The double container is formed by integrally blow-molding an outer preform and an inner preform inside a cavity of a molding die, while fitting the inner preform for forming the inner container into the outer preform for forming the outer container.

As a double container of this type, for example, as shown in Patent Document 1 below, a configuration is known in which a bottom wall portion of a bottom portion has a ground contact portion located at an outer peripheral edge portion, and a topped cylindrical depressed portion located on an inner side in a radial direction from the ground contact portion and recessed upward, and a peripheral wall portion of the depressed portion extends inward in the radial direction as it goes upward via a step portion.

CITATION LIST Patent Document Patent Document 1

Japanese Unexamined Patent Application, First Publication No. 2017-171317

SUMMARY OF INVENTION Technical Problem

However, in the double container of the related art, since the step portion extends continuously over the entire length in a circumferential direction, a flow resistance of a resin material flowing along a stair portion for molding the step portion on the cavity inner surface of the molding die increases at the time of blow molding, and there is a risk that the peripheral wall portion of the depressed portion becomes excessively thick.

In this case, for example, molding defects such as sink marks on the bottom wall portion and excessive thinning of the body portion may occur.

The present invention has been made in view of the circumstances described above, and an object of the present invention is to provide a double container that can reduce the remaining amount of contents which were contained, while curbing molding defects.

Solution to Problem

The present invention adopts the following means to solve the above problems. That is, a first aspect of the present invention is a double container which includes an inner container which decreases in volume and deforms with decrease in contents therein; and an outer container in which the inner container is installed, in which a mouth portion, a body portion, and a bottom portion are disposed in this order from top to bottom along a direction of a bottle axis, and the double container includes an outside air introduction hole which introduces outside air between the outer container and the inner container with decrease in the contents. A bottom wall portion of the bottom portion includes a ground contact portion located at an outer peripheral edge portion, and a depressed portion having a cylindrical shape with a top, the depressed portion which is positioned inside the ground contact portion in the radial direction and recessed upward. A peripheral wall portion of the depressed portion extends inward in a radial direction as it goes upward. A plurality of ridge portions protruding inward in the radial direction are provided on the peripheral wall portion of the depressed portion at intervals in a circumferential direction. The peripheral wall portion of the depressed portion or the plurality of ridge portions extend inward in the radial direction via a step portion as it goes upward.

In this case, the peripheral wall portion of the depressed portion extends inward in the radial direction via the step portion as it goes upwards, or the ridge portion extends inward in the radial directions via the step portion as it goes upward. As a result, in the process of integrally blow-molding the outer preform and the inner preform inside the cavity of the molding die, in the state of fitting the inner preform for forming the inner container into the outer preform for forming the outer container, the flow resistance of the resin material flowing along a stair portion for molding the step portion of the cavity inner surface is increased, and the peripheral wall portion of the depressed portion or the ridge portion can be formed to be thick. As a result, the rigidity of the peripheral wall portion of the depressed portion of the inner container or the rigidity of the ridge portion of the inner container is increased, and when the inner container decreases in volume and deforms due to the reduction of the contents to be contained, the inner container peeling off from the outer container at the peripheral wall portion of the depressed portion can be curbed, and the rigidity of the ridge portions in the inner container is ensured, and when the inner container decreases in volume and deforms with the decrease in the contents to be contained, it is possible to suppress the inner container from peeling off from the outer container in the ridge portion. When the step portion is provided only on the ridge portion, the peripheral wall portion of the depressed portion becoming excessively thick can be curbed without hindering the elongation when blow molding. As a result, for example, it is possible to suppress molding defects such as sink marks in the bottom wall portion and excessive thinning of the body portion. Further, it is possible to increase the adhesion between the inner container and the outer container at the peripheral wall portion of the depressed portion. Accordingly, when the inner container decreases in volume and deforms with the decrease in the contents to be contained, it is possible to suppress the inner container from peeling off from the outer container in the peripheral wall portion of the depressed portion.

As described above, it is possible to reduce the volume of the inner container and deform the inner container as designed with the decrease in contents to be contained, and reduce the remaining amount of the contents.

A second aspect of the present invention is the double container according to the first aspect, in which the peripheral wall portion of the depressed portion extends inward in the radial direction via the step portion as it goes upward, and the plurality of ridge portions which protrude inward in the radial direction and divide the step portion in the circumferential direction are provided on the peripheral wall portion of the depressed portion at intervals in the circumferential direction.

In this case, the peripheral wall portion of the depressed portion extends inward in the radial direction via the step portion as it goes upward. As a result, in the process of integrally blow-molding the outer preform and the inner preform inside the cavity of molding die, in the state of fitting the inner preform for forming the inner container into the outer preform for forming the outer container, the flow resistance of the resin material flowing along the stair portion for molding the step portion of the cavity inner surface is increased, and the peripheral wall portion of the depressed portion can be formed thick. As a result, the rigidity of the peripheral wall portion of the depressed portion of the inner container is increased, and when the inner container decreases in volume and deforms with the decrease in contents to be contained, it is possible to suppress the inner container from peeling off from the outer container in the peripheral wall portion of the depressed portion. Therefore, it is possible to reduce volume of the inner container and deform the inner container as designed with the decrease in contents to be contained, thereby reducing the remaining amount of the contents.

On the peripheral wall portion of the depressed portion, a plurality of ridge portions which protrude inward in the radial direction and divide the step portion in the circumferential direction are provided at intervals in the circumferential direction. As a result, in the process of blow-molding as described above, as the resin material enters the recessed portion of the cavity inner surface for molding the ridge portion, the resin material located in the stair portion is drawn into the recessed portion side and stretched inward in the radial direction, and it is possible to suppress the peripheral wall portion of the depressed portion from becoming excessively thick.

As described above, for example, it is possible to reduce the remaining amount of contents to be contained, while suppressing molding defects such as sink marks in the bottom wall portion and excessive thinning of the body portion.

A third aspect of the present invention is the double container according to the second aspect, in which upper and lower surfaces of a ceiling wall portion of the depressed portion are flat surfaces.

In this case, the upper and lower surfaces of the ceiling wall portion of the depressed portion are flat surfaces. As a result, at the time of blow molding, the resin material is less likely to get caught in the portion of the cavity inner surface in which the depressed portion is molded, and can flow smoothly. Accordingly, it is possible to reliably suppress the peripheral wall portion of the depressed portion from becoming excessively thick, the shapeability is improved, and the step portion and the ridge portion can be formed with high accuracy.

A fourth aspect of the present invention is the double container according to the second aspect or the third aspect, in which, in a wall portion which defines the plurality of ridge portions, a top wall facing the radial direction is positioned inside the step portion in the radial direction.

In this case, the top wall of the ridge portion is located radially inside the step portion. As a result, in the process of blow molding as described above, when the resin material enters the recessed portion of the cavity inner surface, the resin material located in the stair portion can be easily drawn into the recessed portion side. Thus, it is possible to reliably suppress the peripheral wall portion of the depressed portion from becoming excessively thick. Since the top wall of the ridge portion is located radially inside the step portion, the peripheral wall portion of the depressed portion can be provided with many corner portions, and the inner container can easily be caught by the outer container at the peripheral wall portion of the depressed portion. Accordingly, it is possible to reliably suppress the inner container from peeling off from the outer container.

A fifth aspect of the present invention is the double container according to the first aspect, in which the plurality of ridge portions protruding inward in the radial direction are provided at intervals in the circumferential direction on the peripheral wall portion of the depressed portion, and the plurality of ridge portions extend in the radial direction inward via the step portion as it goes upward.

In this case, the ridge portion extends radially inward via the step portion as it goes upward. As a result, in the process of integrally blow-molding the outer preform and the inner preform inside the cavity of the molding die, in the state of fitting the inner preform for forming the inner container into the outer preform for forming the outer container, the flow resistance of the resin material flowing along the stair portion for molding the step portion of the cavity inner surface is increased, and the thickness of the ridge portion can be ensured. As a result, the rigidity of the ridge portion of the inner container is ensured, and when the inner container decreases in volume and deforms due to the reduction of the contents to be contained, it is possible to suppress the inner container from peeling off from the outer container at the ridge portion.

The step portion is provided only on the ridge portion. As a result, the peripheral wall portion of the depressed portion can be suppressed from becoming excessively thick without hindering the elongation when blow molding. As a result, for example, it is possible to suppress molding defects such as sink marks in the bottom wall portion and excessive thinning of the body portion. Further, it is possible to increase the adhesion between the inner container and the outer container at the peripheral wall portion of the depressed portion. Accordingly, when the inner container decreases in volume and deforms with the decrease in the contents to be contained, it is possible to suppress the inner container from peeling off from the outer container in the peripheral wall portion of the depressed portion.

As described above, it is possible to reduce the volume of the inner container and deform the inner container as designed with the decrease in contents to be contained, while suppressing the molding defects, and reduce the remaining amount of the contents.

A sixth aspect of the present invention is the double container according to the fifth aspect, in which the upper and lower surfaces of the ceiling wall portion of the depressed portion are flat surfaces.

In this case, the upper and lower surfaces of the ceiling wall portion of the depressed portion are flat surfaces. As a result, when blow molding, the resin material is easily flow smoothly, without being caught in each portion of the cavity inner surface in which the depressed portion and the ridge portion are molded, shapeability is improved, and the depressed portion and the ridge portion can be formed with high accuracy.

A seventh aspect of the present invention is the double container according to the fifth aspect or the sixth aspect, in which the step portion is positioned inside the peripheral wall portion of the depressed portion in the radial direction.

In this case, the step portion of the ridge portion is positioned radially inside the peripheral wall portion of the depressed portion. As a result, in the process of blow-molding as described above, the resin material can be easily drawn from the portion of the cavity inner surface in which the peripheral wall portion of the depressed portion is molded to the portion in which the ridge portion is molded. As a result, the depressed portion and the ridge portion can be formed with high accuracy.

An eighth aspect of the present invention is the double container according to the first aspect, in which the body portion includes a narrowed portion, the narrowed portion which extends inward in the radial direction from an outside to an inside along a direction of a bottle axis, and which is formed to be elastically deformable, the narrowed portion is formed by connecting a concave curved surface portion and a convex curved surface portion in this order from top to bottom without a step, the concave curved surface portion which is recessed inward in the radial direction, and the convex curved surface portion which bulges outward in the radial direction, and in a vertical cross-sectional view along the direction of the bottle axis, a difference between a radius of curvature of the concave curved surface portion and a radius of curvature of the convex curved surface portion is 20% or less with respect to a larger one of the radii of curvature.

In this case, the narrowed portion of the body portion has a concave curved surface portion. Accordingly, when the concave curved surface portion is pressed radially inward, the narrowed portion can be elastically deformed smoothly radially inward with a light pressing force.

The narrowed portion includes a convex curved surface portion. As a result, for example, compared to a case where the outer container is made of a hard material, the restorability can be improved, while ensuring the flexibility of the narrowed portion, and the narrowed portion can be restored and deformed in a short time after release of the pressure.

As described above, both flexibility (squeeze property) and restorability of the narrowed portion can be achieved. The squeeze property means the property of being able to elastically deform the narrowed portion inward in the radial direction with a light pressing force, and means the property of being able to restore and deform the narrowed portion in a short time after release of the pressure.

In a vertical cross-sectional view along the direction of the bottle axis, the difference between the radii of curvature of each of the concave curved surface portion and the convex curved surface portion is 20% or less of the larger one of each of the radii of curvature. Accordingly, since the difference between the respective radii of curvature is suppressed, when the narrowed portion is pressed radially inward, it is possible to suppress the stress that occurs in the connecting portion between the concave curved surface portion and the convex curved surface portion, and it is possible to suppress the occurrence of local deformation that becomes the starting point of folding in the connecting portion when pressing.

The convex curved surface portion is provided below rather than above the concave curved surface portion. As a result, when the double container (for example, squeeze bottle) is transported in an upright position, on a filling line of the contents, a guide surface of the filling line, which supports the bottom portion side, can be easily brought into contact with the outer peripheral surface of the convex curved surface portion, and the double container (for example, squeeze bottle) falling when being transported can be curbed.

The concave curved surface portion and the convex curved surface portion are provided in this order from top to bottom. As a result, the concave curved surface portion which is pressed radially inward is positioned in the upper part that is stretched and thinned at the time of the biaxial stretch blow molding, and the convex curved surface portion which imparts rigidity to the narrowed portion is provided in the lower part that is thickened. Accordingly, both flexibility (squeeze property) and restorability of the narrowed portion can be reliably achieved.

A ninth aspect of the present invention is the double container according to the eighth aspect, in which the radius of curvature of the concave curved surface portion is greater than the radius of curvature of the convex curved surface portion in the vertical cross-sectional view.

In this case, in the vertical cross-sectional view, the radius of curvature of the concave curved surface portion that is pressed radially inward is greater than the radius of curvature of the convex curved surface portion that imparts rigidity to the narrowed portion. As a result, it is possible to reliably improve the restorability of the narrowed portion, while ensuring the flexibility of the narrowed portion, and it is possible to more reliably achieve both the flexibility (squeeze property) and the restorability of the narrowed portion.

A tenth aspect of the present invention is the double container according to the eighth aspect or the ninth aspect, in which a vertical reinforcement groove extending in the direction of the bottle axis is formed in the convex curved surface portion.

In this case, the vertical reinforcement groove extending in the direction of the bottle axis is formed in the convex curved surface portion. As a result, the rigidity of the convex curved surface portion can be enhanced, and the restorability of the narrowed portion can be reliably improved.

The vertical reinforcement groove which is recessed radially inward is formed in the convex curved surface portion, instead of the ridge portion protruding radially outward. As a result, the guide surface can be easily brought into contact with the outer peripheral surface of the convex curved surface portion when transporting on the filling line, thereby suppressing the double container (for example, squeeze bottle) from falling when transporting.

Advantageous Effects of Invention

According to this invention, it is possible to reduce the remaining amount of contents to be contained, while suppressing molding defects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view including a partial longitudinal section of a double container shown as a first embodiment according to the present invention, viewed from the outside in a radial direction.

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 .

FIG. 3 is a cross-sectional view taken along line of FIG. 2 .

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2 .

FIG. 5 is a side view including a partial longitudinal section of a double container shown as a second embodiment according to the present invention, viewed from the outside in the radial direction.

FIG. 6 is a bottom view of FIG. 5 .

FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6 .

FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 6 .

DESCRIPTION OF EMBODIMENTS First Embodiment

A double container according to a first embodiment of the present invention will be described below with reference to the drawings.

As shown of FIG. 1 , a double container 1 according to the present embodiment includes an inner container 12 that decreases in volume and deforms with the decrease in contents to be contained, and an outer container 11 in which the inner container 12 is installed. The double container 1 may or may not be a squeeze bottle. An outer surface of the inner container 12 is provided on the inner surface of the outer container 11 in a separable manner. In the shown example, the inner container 12 is highly flexible and is laminated on the inner surface of the outer container 11 in a peelable manner.

A gap is provided between a portion of the inner surface of the outer container 11 except a peripheral wall portion of a depressed portion to be described below and a portion of the outer surface of the inner container 12 except the peripheral wall portion of the depressed portion to be described below.

The double container 1 is formed by integrally blow-molding an outer preform and an inner preform in a state in which the inner preform for forming the inner container is fitted into the outer preform for forming the outer container 11. That is, the double container 1 is a biaxially stretched blow container.

The material of the inner container 12 and the outer container 11 is a synthetic resin material, and may be the same material or different materials. Examples of synthetic resin materials include polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), nylon (polyamide), and ethylene-vinyl alcohol copolymer (EVOH).

The double container 1 has a mouth portion 13, a shoulder portion 15, a body portion 16 and a bottom portion 14. The mouth portion 13, the shoulder portion 15, the body portion 16 and the bottom portion 14 are disposed coaxially with a common axis in this order.

Hereinafter, the common axis will be referred to as a bottle axis O, the mouth portion 13 side of the double container 1 along the bottle axis O will be referred to as an upper side, and the bottom portion 14 side of the double container 1 will be referred to as a lower side. When viewed from the direction of the bottle axis O, a direction intersecting the bottle axis O is referred to as a radial direction, and a direction rotating around the bottle axis O is referred to as a circumferential direction.

The mouth portion 13 of the double container 1 is formed by laminating the mouth portion of the inner container 12 and the mouth portion of the outer container 11. The shoulder portion 15 of the double container 1 is formed by laminating the shoulder portion of the inner container 12 and the shoulder portion of the outer container 11. The body portion 16 of the double container 1 is configured by laminating the body portion of the inner container 12 and the body portion of the outer container 11. The bottom portion 14 of the double container 1 is formed by laminating the bottom portion of the inner container 12 and the bottom portion of the outer container 11.

In the following description, unless otherwise specified, both the inner container 12 and the outer container 11 have the same shape.

The size of the double container 1 in the direction of the bottle axis O is, for example, 115 mm or more and 220 mm or less. The inner capacity of the double container 1 is, for example, 150 ml or more and 600 ml or less. In the shown example, the size of the double container 1 in the direction of the bottle axis O is about 180 mm, and the inner capacity of the double container 1 is 330 ml.

The mouth portion 13 of the double container 1 is formed in a cylindrical shape extending upward from an upper end portion of the shoulder portion 15.

A flange portion which protrudes radially outward and extends continuously over the entire length in the circumferential direction is formed at the upper end portion of the mouth portion of the inner container 12. The flange portion is placed on an upper opening edge of the mouth portion of the outer container 11.

A male threaded portion 18 to which a cap (not shown) is screwed and a sealed protrusion 19 to which a peripheral wall portion of the cap (not shown) is externally fitted are formed in this order on the outer peripheral surface of the mouth portion of the outer container 11 from top to bottom. The sealed protrusion 19 protrudes radially outward from the mouth portion of the outer container 11, and extends continuously over the entire length in the circumferential direction. An airtight seal is formed between the outer peripheral surface of the sealed protrusion 19 and the inner peripheral surface of the peripheral wall portion of the cap (not shown).

The cap may be undercut-fitted to the mouth portion of the outer container 11.

An outside air introduction hole 17 which introduces the outside air into the space between the outer container 11 and the inner container 12 with the decrease in contents is formed at the mouth portion of the outer container 11. The outside air introduction hole 17 is positioned on the radially outermost side in the sealed protrusion 19, and is positioned above the sealing surface that extends continuously over the entire length in the circumferential direction.

A formation position of the outside air introduction hole 17 is not limited to the mouth portion of the outer container 11, and may be, for example, the body portion, the shoulder portion or the bottom portion of the outer container 11 other than the mouth portion. Alternatively, the formation position may be between the upper end opening edge of the mouth portion of the outer container 11 and the lower surface of the flange portion of the mouth portion of the inner container 12.

The shoulder portion 15 extends radially outward from the lower end portion of the mouth portion 13 downward. A plurality of vertical partition grooves 15 a are formed in the shoulder portion 15 at intervals in the circumferential direction. The shoulder portion 15 is formed in a curved surface shape that protrudes outward in the radial direction.

The bottom portion 14 is formed in a bottomed cylindrical shape. An outer peripheral surface of the peripheral wall portion 14 b of the bottom portion 14 extends straight in the direction of the bottle axis O. A peripheral groove 14 a is formed on the outer peripheral surface of the peripheral wall portion 14 b of the bottom portion 14 to extend continuously over the entire length in the circumferential direction.

An upper end portion 16 a of the body portion 16 extends straight in the direction of the bottle axis O. The outer peripheral surfaces of each of the upper end portion 16 a of the body portion 16 and the peripheral wall portion 14 b of the bottom portion 14 have the maximum outer diameter portion having the largest outer diameter in the double container 1. The outer diameter of the maximum outer diameter portion is, for example, 58 mm or more and 74 mm or less. In the shown example, the outer diameter of the maximum outer diameter portion of the double container 1 is approximately 66 mm.

A portion of the body portion 16 located below the upper end portion 16 a is a narrowed portion 21 extending radially inward from the outside to the inside along the direction of the bottle axis O. That is, the body portion 16 has a narrowed portion 21 that extends inward in the radial direction from the outside toward the inside along the direction of the bottle axis O and is formed to be elastically deformable. The size of the narrowed portion 21 in the direction of the bottle axis O is equal to or greater than half the size of the body portion 16 in the direction of the bottle axis O. The size of the narrowed portion 21 in the direction of the bottle axis O is greater than the sizes of each of the mouth portion 13, the shoulder portion 15, and the bottom portion 14 in the direction of the bottle axis O.

A radial distance between the deepest portion 21 b of the narrowed portion 21 located on the radially innermost side and the maximum outer diameter portion of the double container 1, that is, a depth of the narrowed portion 21 is, for example, 2% or more and 10% or less of the outer diameter of the maximum outer diameter portion of the double container 1. In the shown example, the depth of the narrowed portion 21 is approximately 6.1% of the outer diameter of the maximum outer diameter portion of the double container 1. The outer diameter of the upper end portion 16 a of the body portion 16 is greater than the outer diameter of the upper end portion of the narrowed portion 21, and the upper end portion 16 a of the body portion 16 and the narrowed portion 21 are connected to each other via a step portion 16 d.

The narrowed portion 21 is configured such that a concave curved surface portion 16 b that is recessed radially inward is connected to a convex curved surface portion 16 c that bulges radially outward in this order from top to bottom without a step.

The size of the concave curved surface portion 16 b in the direction of the bottle axis O is greater than the size of the convex curved surface portion 16 c in the direction of the bottle axis O. The size of the concave curved surface portion 16 b in the direction of the bottle axis O may be equal to or less than the size of the convex curved surface portion 16 c in the direction of the bottle axis O.

In a vertical cross-sectional view along the direction of the bottle axis O, a difference between radii of curvature R1 and R2 of each of the concave curved surface portion 16 b and the convex curved surface portion 16 c is 20% or less of the larger one of the radii of curvature R1 and R2, and preferably 10% or less. In the shown example, the radius of curvature R1 (approximately 110 mm) of the concave curved surface portion 16 b is greater than the radius of curvature R2 (approximately 100 mm) of the convex curved surface portion 16 c in the vertical cross-sectional view. In addition, in the vertical cross-sectional view, the radius of curvature R1 of the concave curved surface portion 16 b may be equal to or less than the radius of curvature R2 of the convex curved surface portion 16 c.

In the vertical cross-sectional view, the radii of curvature R1 and R2 of the concave curved surface portion 16 b and the convex curved surface portion 16 c are, for example, 80 mm or more and 120 mm or less.

A vertical reinforcement groove 28 extending in the direction of the bottle axis O is formed in the convex curved surface portion 16 c. The vertical reinforcement groove 28 may not be formed in the convex curved surface portion 16 c.

The vertical reinforcement groove 28 is positioned below the deepest portion 21 b of the narrowed portion 21. A lower end portion of the vertical reinforcement groove 28 is positioned at the lower end portion 21 a of the narrowed portion 21. In the shown example, the vertical reinforcement groove 28 reaches the lower end edge of the narrowed portion 21. The inner surface of the vertical reinforcement groove 28 has a concave curved linear shape in a cross-sectional view orthogonal to the bottle axis O. The depth of both end portions of the vertical reinforcement groove 28 in the direction of the bottle axis O becomes shallower toward the outside in the direction of the bottle axis O. A plurality of vertical reinforcement grooves 28 are formed in the convex curved surface portion 16 c at intervals in the circumferential direction.

At least the narrowed portion 21 (body portion 16) of the outer container 11 can be subjected to squeeze deformation (elastic deformation), and the inner container 12 shrinks and deforms with the squeeze deformation of the outer container 11. The body portion 16, the shoulder portion 15 and the bottom portion 14 are continuous in the direction of the bottle axis O without a step. The outer container 11 may be formed not to be elastically deformable.

Here, the bottom wall portion 22 of the bottom portion 14 includes a ground contact portion 23 positioned at the outer peripheral edge portion, and a depressed portion 24 having a cylindrical shape with a top positioned radially inside the ground contact portion 23 and recessed upward. The ground contact portion 23 and the depressed portion 24 are disposed coaxially with the bottle axis O.

Upper and lower surfaces of a ceiling wall portion 29 of the depressed portion 24 are flat surfaces as shown of FIGS. 2 to 4 .

A peripheral wall portion 25 of the depressed portion 24 extends inward in the radial direction via the step portion 26 as it goes upward. The step portion 26 is formed in a flat plate shape facing the direction of the bottle axis O. A plurality of step portions 26 are provided at intervals in the direction of the bottle axis O. The radial sizes of each of the plurality of step portions 26 are equal to each other. The radial sizes of each of the plurality of step portions 26 may be appropriately changed, for example, to be smaller as they are positioned upward.

On the peripheral wall portion 25 of the depressed portion 24, a plurality of ridge portions 27 which protrude inward in the radial direction and divide the step portion 26 in the circumferential direction are provided at intervals in the circumferential direction. Four or more even numbered ridge portions 27 are provided at equal intervals in the circumferential direction. Three or more odd-numbered ridge portions 27 may be provided at equal intervals in the circumferential direction. The interval between the ridge portions 27 adjacent to each other in the circumferential direction is equal to the sizes of the ridge portions 27 in the circumferential direction.

The circumferential size of the ridge portion 27 decreases upward. The ridge portions 27 are provided over the entire length of the peripheral wall portion 25 of the depressed portion 24 in the direction of the bottle axis O. The upper end edge of the ridge portion 27 reaches the outer peripheral edge of the ceiling wall portion 29 of the depressed portion 24.

The ridge portion 27 includes a top wall 31 facing in the radial direction, and a pair of side walls 32 which extend radially inward from the peripheral wall portion 25 of the depressed portion 24 and are separately connected to both end portions of the top wall 31 in the circumferential direction.

The circumferential interval between the pair of side walls 32 becomes smaller toward the inner side in the radial direction. In a cross-sectional view orthogonal to the bottle axis O, the side wall 32 and the peripheral wall portion 25 of the depressed portion 24 are substantially orthogonal to each other.

The top wall 31 of the ridge portion 27 is located radially inside the step portion 26. The respective radial distances between the top wall 31 and the plurality of step portions 26 are equal to each other. An inclination angle θ1 of the upper portion 31 a of the top wall 31 to the bottle axis O is smaller than an inclination angle θ2 of the lower portion 31 b to the bottle axis O. A connecting portion 31 c of the top wall 31 between the upper portion 31 a and the lower portion 31 b is formed in a curved surface protruding radially inward. The lengths of each of the upper portion 31 a and the lower portion 31 b are equal to each other.

As described above, according to the double container 1 according to the present embodiment, the peripheral wall portion 25 of the depressed portion 24 extends inward in the radial direction via the step portion 26 as it goes upward. As a result, in the process of integrally blow-molding the outer preform and the inner preform inside the cavity of molding die, in the state of fitting the inner preform for forming the inner container 12 into the outer preform for forming the outer container 11, the flow resistance of the resin material flowing along the stair portion for molding the step portion 26 of the cavity inner surface is increased, and the peripheral wall portion 25 of the depressed portion 24 can be formed thick.

As a result, when the rigidity of the peripheral wall portion of the depressed portion of the inner container 12 is increased, and the inner container 12 decreases in volume and deforms with the decrease in contents to be contained, it is possible to suppress the inner container 12 from peeling off from the outer container 11 in the peripheral wall portion 25 of the depressed portion 24. Therefore, it is possible to reduce volume of the inner container 12 and deform the inner container 12 as designed with the decrease in contents to be contained, thereby reducing the remaining amount of the contents.

On the peripheral wall portion 25 of the depressed portion 24, a plurality of ridge portions 27 which protrude inward in the radial direction and divide the step portion 26 in the circumferential direction are provided at intervals in the circumferential direction. As a result, in the process of blow-molding as described above, as the resin material enters the recessed portion of the cavity inner surface for molding the ridge portion 27, the resin material located in the stair portion is drawn into the recessed portion side and stretched inward in the radial direction, and it is possible to suppress the peripheral wall portion 25 of the depressed portion 24 from becoming excessively thick.

As described above, for example, it is possible to reduce the remaining amount of contents to be contained, while suppressing molding defects such as sink marks in the bottom wall portion 22 and excessive thinning of the body portion 16.

The upper and lower surfaces of the ceiling wall portion 29 of the depressed portion 24 are flat surfaces. As a result, at the time of blow molding, the resin material is less likely to get caught in the portion of the cavity inner surface in which the depressed portion 24 is molded, and can flow smoothly. Accordingly, it is possible to reliably suppress the peripheral wall portion 25 of the depressed portion 24 from becoming excessively thick, the shapeability is improved, and the step portion 26 and the ridge portion 27 can be formed with high accuracy.

The top wall 31 of the ridge portion 27 is located radially inside the step portion 26. As a result, in the process of blow molding as described above, when the resin material enters the recessed portion of the cavity inner surface, the resin material located in the stair portion can be easily drawn into the recessed portion. Thus, it is possible to reliably suppress the peripheral wall portion 25 of the depressed portion 24 from becoming excessively thick.

The top wall 31 of the ridge portion 27 is located radially inside the step portion 26. As a result, the peripheral wall portion 25 of the depressed portion 24 can be provided with many corner portions, and the inner container 12 can easily be caught by the outer container 11 at the peripheral wall portion 25 of the depressed portion 24. Accordingly, it is possible to reliably suppress the inner container 12 from peeling off from the outer container 11.

The narrowed portion 21 of the body portion 16 has a concave curved surface portion 16 b. Accordingly, when the concave curved surface portion 16 b is pressed radially inward, the narrowed portion 21 can be elastically deformed smoothly radially inward with a light pressing force.

The narrowed portion 21 includes a convex curved surface portion 16 c. As a result, for example, compared to a case where the outer container 11 is made of a hard material, the restorability can be improved while ensuring the flexibility of the narrowed portion 21, and the narrowed portion 21 can be restored and deformed in a short time after the pressure is released.

As described above, both flexibility (squeeze property) and restorability of the narrowed portion 21 can be achieved.

In a vertical cross-sectional view along the direction of the bottle axis O, the difference between the radii of curvature R1 and R2 of each of the concave curved surface portion 16 b and the convex curved surface portion 16 c is 20% or less of the larger one of each of the radii of curvature. Accordingly, the difference between the respective radii of curvature R1 and R2 is suppressed. As a result, when the narrowed portion 21 is pressed radially inward, it is possible to suppress the stress that occurs in the connecting portion between the concave curved surface portion 16 b and the convex curved surface portion 16 c, and it is possible to suppress the occurrence of local deformation that becomes the starting point of folding in the connecting portion when pressing.

The convex curved surface portion 16 c is provided below rather than above the concave curved surface portion 16 b. As a result, when the double container 1 is transported at an upright position on a filling line of the contents, a guide surface of the filling line, which supports the bottom portion 14 side, can be easily brought into contact with the outer peripheral surface of the convex curved surface portion 16 c, and it is possible to suppress the double container 1 (for example, squeeze bottle) from falling when transporting.

The concave curved surface portion 16 b and the convex curved surface portion 16 c are provided in this order from top to bottom. As a result, the concave curved surface portion 16 b which is pressed radially inward is positioned in the upper part that is stretched and thinned at the time of the biaxial stretch blow molding, and the convex curved surface portion 16 c which imparts rigidity to the narrowed portion 21 is provided in the lower part that is thickened. Accordingly, both flexibility (squeeze property) and restorability of the narrowed portion 21 can be reliably achieved.

In the vertical cross-sectional view, the radius of curvature R1 of the concave curved surface portion 16 b that is pressed radially inward is greater than the radius of curvature R2 of the convex curved surface portion 16 c that imparts rigidity to the narrowed portion 21. As a result, it is possible to reliably improve the restorability of the narrowed portion 21 while ensuring the flexibility of the narrowed portion 21, and it is possible to more reliably achieve both the flexibility (squeeze property) and the restorability of the narrowed portion 21.

A vertical reinforcement groove 28 extending in the direction of the bottle axis O is formed in the convex curved surface portion 16 c. As a result, the rigidity of the convex curved surface portion 216 c can be enhanced, and the restorability of the narrowed portion 21 can be reliably improved.

The vertical reinforcement groove 28 which is recessed radially inward is formed in the convex curved surface portion 16 c, instead of the ridge portion protruding radially outward. As a result, the guide surface can be easily brought into contact with the outer peripheral surface of the convex curved surface portion 16 c when transporting on the filling line, thereby suppressing the double container 1 (for example, squeeze bottle) from falling when transporting.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

The body portion 16 may extend straight in the direction of the bottle axis O, for example, without having the narrowed portion 21. The top wall 31 of the ridge portion 27 may be connected to the radially inner end portion of the step portion 26 in the circumferential direction.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with known constituent elements without departing from the scope of the present invention, and the above-described embodiment and the above-described modifications may be combined as appropriate.

Second Embodiment

A double container according to a second embodiment will be described below with reference to the drawings. A double container 101 according to this embodiment is shown of FIG. 5 . The double container 101 may or may not be a squeeze bottle. However, the contents of the second embodiment that are different from those of the first embodiment will be mainly described. Therefore, in the double container 101 of the second embodiment, the same or equivalent configurations as those of the double container 1 of the above-described first embodiment are denoted by the same reference numerals, and the description thereof will be simplified or omitted.

Here, a bottom wall portion 122 of a bottom portion 14 includes a ground contact portion 123 positioned at the outer peripheral edge portion, a depressed portion 124 having a cylindrical shape with a top positioned radially inside the ground contact portion 123 and recessed upward, and a connecting portion 122 a that connects the ground contact portion 123 and the depressed portion 124.

The ground contact portion 123, the depressed portion 124, and the connecting portion 122 a are disposed coaxially with the bottle axis O. The connecting portion 122 a is positioned above the ground contact portion 123 and extends upward as it goes radially inward. The bottom wall portion 122 may not have the connecting portion 122 a.

The upper and lower surfaces of the ceiling wall portion 129 of the depressed portion 124 are flat surfaces facing the direction of the bottle axis O.

A peripheral wall portion 125 of the depressed portion 124 extends inward in the radial direction as it goes upward. A peripheral wall portion 125 of the depressed portion 124 is formed in a curved surface shape protruding outward in the radial direction.

A plurality of ridge portions 127 protruding radially inward are provided on the peripheral wall portion 125 of the depressed portion 124 at intervals in the circumferential direction.

As shown of FIG. 6 , three or more odd-numbered ridge portions 127 are provided at equal intervals in the circumferential direction. Further, four or more even-numbered ridge portions 127 may be provided at equal intervals in the circumferential direction. The interval between the ridge portions 127 adjacent to each other in the circumferential direction is equal to the size of the ridge portions 127 in the circumferential direction.

The circumferential size of the ridge portion 127 decreases upward. As shown of FIGS. 7 and 8 , the ridge portion 127 is provided over the entire length of the peripheral wall portion 125 of the depressed portion 124 in the direction of the bottle axis O. An upper end edge of the ridge portion 127 reaches an outer peripheral edge of the ceiling wall portion 129 of the depressed portion 124.

As shown of FIG. 6 , the ridge portions 127 is defined by a top wall 131 facing in the radial direction, and a pair of side walls 132 which extend radially inward from the peripheral wall portion 125 of the depressed portion 124 and separately connected to both end portions of the top wall 131 in the circumferential direction.

The circumferential interval between the pair of side walls 132 decreases as it goes radially inward. In a cross-sectional view orthogonal to the bottle axis O, the side wall 132 and the peripheral wall portion 125 of the depressed portion 124 are substantially orthogonal to each other.

Further, in the present embodiment, the ridge portion 127 extends inward in the radial direction via the step portion 126 as it goes upward.

As shown of FIGS. 7 and 8 , the step portion 126 is formed in a curved surface shape that is recessed outward in the radial direction. The step portion 126 is positioned radially inside the peripheral wall portion 125 of the depressed portion 124.

In the vertical cross-sectional view, a length of the upper portion 127 a positioned above the step portion 126 of the ridge portion 127 is shorter than the length of the lower portion 127 b positioned below the step portion 126. The upper portion 127 a and the lower portion 127 b are formed in a curved surface shape that protrudes inward in the radial direction. In the vertical cross-sectional view, the radius of curvature of the lower portion 127 b is smaller than the radius of curvature of the upper portion 127 a and greater than the radius of curvature of the step portion 126. In the vertical cross-sectional view, the lower portion 127 b protrudes inward in the radial direction with respect to a straight line L that circumscribes the upper portion 127 a.

As described above, according to the double container 101 of the present embodiment, the ridge portions 127 extend radially inward via the step portions 126 as they go upward. As a result, in the process of integrally blow-molding the outer preform and the inner preform inside the cavity of the molding die, in the state of fitting the inner preform for forming the inner container 12 into the outer preform for forming the outer container 11, the flow resistance of the resin material flowing along the stair portion for molding the step portion 126 of the cavity inner surface is increased, and the thickness of the ridge portion 127 can be ensured.

As a result, the rigidity of the ridge portion of the inner container 12 is ensured, and when the inner container 12 decreases in volume and deforms due to the reduction of the contents to be contained, it is possible to suppress the inner container 12 from peeling off from the outer container 11 at the ridge portion 127.

The step portion 126 is provided only on the ridge portion 127. As a result, the peripheral wall portion 125 of the depressed portion 124 can be suppressed from becoming excessively thick without hindering the elongation when blow molding.

As a result, for example, it is possible to suppress molding defects such as sink marks in the bottom wall portion 122 and excessive thinning of the body portion 16. Further, it is possible to increase the adhesion between the inner container 12 and the outer container 11 at the peripheral wall portion 125 of the depressed portion 124, and when the inner container 12 decreases in volume and deforms with the decrease in the contents to be contained, it is possible to suppress the inner container 12 from peeling off from the outer container 11 in the peripheral wall portion 125 of the depressed portion 124.

As described above, it is possible to reduce the volume of the inner container 12 and deform the inner container 12 as designed with the decrease in contents to be contained, while suppressing the molding defects, and reduce the remaining amount of the contents.

The upper and lower surfaces of the ceiling wall portion 129 of the depressed portion 124 are flat surfaces. As a result, when blow molding, the resin material easily flows smoothly without being caught in each portion of the cavity inner surface in which the depressed portion 124 and the ridge portion 127 are molded, shapeability is improved, and the depressed portion 124 and the ridge portion 127 can be formed with high accuracy.

The step portion 126 of the ridge portion 127 is positioned radially inside the peripheral wall portion 125 of the depressed portion 124. As a result, in the process of blow-molding as described above, the resin material can be easily drawn from the portion of the cavity inner surface in which the peripheral wall portion 125 of the depressed portion 124 is molded to the portion in which the ridge portion 127 is molded. As a result, the depressed portion 124 and the ridge portion 127 can be formed with high accuracy.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

The body portion 16 may extend straight in the direction of the bottle axis O, for example, without having the narrowed portion 121.

A plurality of step portions 126 may be provided at intervals in the direction of the bottle axis O.

The step portion 126 may be continuous with the peripheral wall portion 125 of the depressed portion 124 in the circumferential direction.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with known constituent elements without departing from the scope of the present invention, and the above-described embodiment and the above-described modifications may be combined as appropriate.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to reduce the remaining amount of contents to be contained, while suppressing molding defects.

REFERENCE SIGNS LIST

1, 101 Double container

11 Outer container

12 Inner container

13 Mouth portion

14 Bottom portion

16 Body portion

17 Outside air introduction hole

22, 122 Bottom wall portion

23, 123 Ground contact portion

24, 124 Depressed portion

25, 125 Peripheral wall portion of depressed portion

26, 126 Step portion

27, 127 Ridge portion

29, 129 Ceiling portion of the depressed portion

31, 131 Top wall of ridge portion

32, 132 side wall of the ridge portion

16 b Concave curved surface portion

16 c Convex curved surface portion

21 Narrowed portion

28 Vertical reinforcement groove

O Bottle axis

R1 Radius of curvature of concave curved surface portion

R2 Radius of curvature of convex curved surface portion 

1. A double container comprising: an inner container which decreases in volume and deforms with decrease in contents therein; and an outer container in which the inner container is installed, wherein a mouth portion, a body portion, and a bottom portion are disposed in this order from top to bottom along a direction of a bottle axis, the double container includes an outside air introduction hole which introduces outside air between the outer container and the inner container with decrease in the contents, a bottom wall portion of the bottom portion includes a ground contact portion located at an outer peripheral edge portion, and a depressed portion having a cylindrical shape with a top, the depressed portion which is positioned inside the ground contact portion in a radial direction and recessed upward, a peripheral wall portion of the depressed portion extends inward in the radial direction as it goes upward, a plurality of ridge portions protruding inward in the radial direction are provided on the peripheral wall portion of the depressed portion at intervals in a circumferential direction, and the peripheral wall portion of the depressed portion or the plurality of ridge portions extend inward in the radial direction via a step portion as it goes upward.
 2. The double container according to claim 1, wherein the peripheral wall portion of the depressed portion extends inward in the radial direction via the step portion as it goes upward, and the plurality of ridge portions which protrude inward in the radial direction and divide the step portion in the circumferential direction are provided on the peripheral wall portion of the depressed portion at intervals in the circumferential direction.
 3. The double container according to claim 2, wherein upper and lower surfaces of a ceiling wall portion of the depressed portion are flat surfaces.
 4. The double container according to claim 2, wherein in a wall portion which defines the plurality of ridge portions, a top wall facing the radial direction is positioned inside the step portion in the radial direction.
 5. The double container according to claim 1, wherein the plurality of ridge portions extend inward in the radial direction via the step portion as it goes upward.
 6. The double container according to claim 5, wherein upper and lower surfaces of a ceiling wall portion of the depressed portion are flat surfaces.
 7. The double container according to claim 5, wherein the step portion is positioned inside the peripheral wall portion of the depressed portion in the radial direction.
 8. The double container according to claim 1, wherein the body portion has a narrowed portion, the narrowed portion which extends inward in the radial direction from an outside to an inside along a direction of a bottle axis, and which is formed to be elastically deformable, the narrowed portion is formed by connecting a concave curved surface portion and a convex curved surface portion in this order from top to bottom without a step, the concave curved surface portion which is recessed inward in the radial direction, and the convex curved surface portion which bulges outward in the radial direction, and in a vertical cross-sectional view along the direction of the bottle axis, a difference between a radius of curvature of the concave curved surface portion and a radius of curvature of the convex curved surface portion is 20% or less with respect to a larger one of the radii of curvature.
 9. The double container according to claim 8, wherein the radius of curvature of the concave curved surface portion is greater than the radius of curvature of the convex curved surface portion in the vertical cross-sectional view.
 10. The double container according to claim 8, wherein a vertical reinforcement groove extending in the direction of the bottle axis is formed in the convex curved surface portion. 